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Full text of "The Morphology And Evolution Of The Apes And Man"

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171            MORPHOLOGY AND EVOLUTION
MUSCLES OF THE BACK.
The trapezius is built on the same general plan in the larger Siiniidae and Man, for its origin extends from the occiput to the lower dorsal region; the cervical part is, however, relatively shorter in the Apes. In the Gibbon there is no occipital origin, the muscle arising from the lower cervical and upper seven dorsal spinous processes. In the Gorilla and Orang the occipital origin is most extensive, for it extends out to the insertion of the sterno-mastoid; but the dorsal spinal origin is variable.
In the Chimpanzee it arises from the inner third of the occipital crest, the inion and the tips of the spines of the cervical and dorsal vertebrae and supraspinous ligament. No ligarnentum nuchse exists. Some authors give it as arising from the first ten to twelve spines. The lower border may be fused with the latissimus dorsi. The entire origin is muscular. It is inserted into the outer third of the posterior border of the clavicle, some fibres passing into the deltoid, the outer border of the acromion and the whole length of the spine of the scapula.
The latissimus dorsi arises from a variable number of dorsal spinous processes and ribs, from the posterior lamella of the lumbar fascia and from the anterior part of the outer lip of the iliac crest. It never arises from the scapula in the Apes. The observations regarding the origin which have been recorded are shown in the table on next page.
The fibres converge to a ribbon-like tendon, which is inserted into the floor of the bicipital groove on the